Cold water-soluble polysaccharides from tetrasporic Pterocladia capillacea.

Cold water extraction of tetrasporic Pterocladia capillacea led to the isolation of a product which was characterized and further treated with Cetrimide. The complexed material was subjected to fractional solubilization in solutions of increasing sodium chloride concentration and six fractions were separated. The two major products obtained, one soluble in Cetrimide solution, the other soluble in 0.5 M sodium chloride, were subjected to structural studies, carried out by methylation analysis and 13C NMR spectroscopy. The results obtained indicated for the former a backbone mainly constituted by alternating 3-linked beta-D-galactose units and 4-linked 3,6-anhydro-alpha-L-galactose residues, but with other structural features probably responsible for its non-gelling properties. The acidic fraction is a complex polysaccharide sulphated mainly on C-6 of the beta-D-galactose units and on C-3 of the alpha-L-galactose residues.